Field of the Invention
The present invention relates to a chemical analyzing apparatus that determines the kind and concentration of a substance dissolved in a liquid and more particularly to a chemical analyzing apparatus that analyzes components of humor and water.
Among conventional chemical analyzing apparatus is a chemical analyzing apparatus of U.S. Pat. No. 4,451,433. This chemical analyzing apparatus comprises a calorimetric unit for analyzing and determining protein and enzyme contained in blood and components of urine and an ion analyzing unit for analyzing ions in blood. This chemical analyzing apparatus has a processing rate of several hundred tests per hour and, in a large type, 9000 tests or more per hour. The colorimetric unit in particular has a large number of reaction containers or cells placed on a circumference of a turntable mounted on the upper surface of an apparatus body and performs overlap processing to mix, react and measure samples successively.
This apparatus comprises: an automatic sample/reagent supply mechanism for supplying samples and reagents to reaction cells; a holder for holding several tens of kinds of reagent containers; an automatic agitation mechanism for agitating the samples and reagents in the reaction cells; a measuring device for measuring characteristics of the samples during or after reaction; an automatic cleansing mechanism for drawing by suction and discharging the samples after characteristic measurements are made and for washing the reaction cells; an automatic cleansing mechanism for washing the automatic sample/reagent supply mechanism; and a controller for controlling the operations of these mechanisms and devices.
There are several tens of kinds of colorimetric test items and, even in normal assays, each sample is tested for at least about ten kinds of inspection items. Conventional reagent supply mechanisms use a reagent pipetting mechanism. The reagent pipetting mechanism comprises mainly a nozzle for drawing reagent into it and holding the reagent there, a mechanism for moving the nozzle three-dimensionally, and a suction/delivery control pump for drawing and discharging the reagent into and out of the nozzle.
To transmit the suction/delivery operation of the pump to the nozzle with good response, pure water (hereinafter referred to as system water) is filled in a pipe between the pump and the nozzle. The system water and the reagent are separated by air to avoid their mixing. This air layer is formed by drawing air into the nozzle before drawing the reagent into it.
The supply of reagent is performed in the following manner. First, the nozzle is dipped into a reagent container by a three-dimensional transfer mechanism to draw by suction a specified amount of reagent into it. The nozzle is moved away from the reagent container and placed over a reaction cell into which the reagent is discharged. After the reagent is discharged, the interior and exterior of the nozzle is washed with cleansing liquid in a nozzle washing bath to avoid contaminating the next reagent. Because the path which the nozzle of the reagent pipetting mechanism travels is fixed, a holder for holding the reagent containers is provided below the path of the nozzle.
Another example of the conventional technology is an automatic analyzing apparatus described in JP-A-63-131066. This example is similar to the above-described conventional technology in terms of sampling, mixing and reaction, photometry, and the washing of reaction cells but differs from it in the reagent supply method.
With a reduction in apparatus size taken as the first objective, this conventional technology arranges the reagent container holder above the reaction cell holder so that the reaction cells and the reagent containers overlap at two predetermined points. Hence, the delivery of reagent into the reaction cell is done by a piston formed integral with the side surface of each reagent container. The piston is actuated by a piston rod actuator provided at a reagent delivery position.
At the delivery position, the piston rod actuator for the reagent container is temporarily connected to the piston rod. Next, the piston rod is pulled up to draw the reagent from the reagent container into the piston. When it reaches the upper limit of its stroke, the piston rod meshes with a gear that rotates the piston through 180 degrees. At this time, the rotation of the piston closes a hole which was open to draw in the reagent, and opens a hole connecting to a delivery port. As the piston rod is driven down, the reagent in the piston is discharged through the hole into the reaction cell.
The above-mentioned conventional technology has the following three drawbacks.
First, the reduction in the size of the apparatus and in the space required is not sufficient. Second, contamination between different reagents cannot be prevented completely. Third, the amount of pure water used is large, requiring a pure water making device outside the apparatus and periodical replacement of the filter and other components, which in turn necessitates additional costs and installation space. These problems are described in detail as follows.
The reason that the reduction in size and space is difficult in the conventional technologies will be explained. The first conventional technology described above picks up a sample and a reagent by the pipetting mechanism, which requires all elements associated with the operations, such as sampling, washing, suction and discharge, to be arranged on a plane beneath the movement locus of the pipetter nozzle. To avoid interference among elements, a certain degree of space is required. Furthermore, the fact that these two-dimensionally arranged elements are large in numbers and kinds also contributes to hindering a reduction in size.
A similar problem also exists as to the reduction in a space around the agitation mechanism. The conventional technology performs stirring with spatulas and thus requires a cleansing device for spatulas. It is also necessary to install the cleansing device so that it does not interfere with the movement locus of the spatulas, making the space reduction difficult. Because the reagent pipetting mechanism and the agitation mechanism using spatulas are employed, there are limitations to the relative positions among the elements, which makes it impossible to adopt a compact arrangement, rendering the size reduction difficult.
The second conventional technology crosses the reagent holder and the reaction cell holder to realize a certain degree of size reduction. With the agitation mechanism, however, the situation is no better than the first conventional technology and, when the apparatus is considered as a whole, the size reduction is not satisfactory.
Next, the problem of mutual contamination will be described. The mutual contaminations occur because different samples and reagents are handled by a common supply means.
The first conventional technology has a sampling mechanism that draws in and discharges, or pipettes, samples successively with a single nozzle. Further, the mutual contamination is also likely to occur in the reagent pipetting mechanism that pipettes several tens of reagents with a single nozzle and in the agitation mechanism that stirs the samples and reagents in the reaction cells.
The reaction cells can be thoroughly washed clean because after photometry they are washed with a cleansing liquid a plurality of times. As to the sample and reagent nozzles and the agitation mechanism, because they are washed in as short a duration of time as one cycle, thorough cleansing is difficult. In the case of biochemistry in particular, mutual contaminations by residual reagents have a significantly greater effect on the result of assay than residual samples.
Therefore, the essential point is the prevention of mutual contamination from the nozzle of the reagent pipetting mechanism and the spatulas of the agitation mechanism. In the second conventional technology a reagent delivery pump is provided for each reagent cell to prevent the mutual contamination by the reagent supply system. However, the agitation mechanism employs a conventional mechanism using spatulas and still has a problem of mutual contamination.
The next problem to be solved is a reduction in the amount of pure water used and simplification of associated facilities. The pure water is used mostly as a cleansing liquid as described in the explanation of the second problem. Hence, reducing the amount of cleansing liquid will result in a significant reduction in the amount of pure water used. With the conventional technologies, however, a large amount of cleansing liquid needs to be used to prevent the mutual contamination. The nozzles of the sampling mechanism and the reagent pipetting mechanism and the spatulas of the agitation mechanism, in particular, are washed with an increased flow of cleansing liquid in order to improve the cleansing capability and thereby complete the washing operation in a short period of time.
The necessity to ensure the required analyzing performance does not allow the cleansing liquid to be reduced in amount. The required amount of pure water at present is several tens of liters per hour. To meet this requirement a pure water making device of filter type is installed separately outside the apparatus and connected through water piping to the apparatus. The pure water making device and its associated piping require additional space and costs the user additional initial investments. Maintaining the pure water making device requires periodical replacement of expensive filters, which is a substantial burden for the user.